1. Field of the Invention
The present invention relates generally to the making of collagen membranes and, more specifically, to the making of edible collagen membranes for wrapping food products, such as hams and the like.
2. Description of the Related Art
Collagen membranes (a.k.a.: films, foils, etc.) are used in variety of applications, such as illustrated in U.S. Pat. No. 5,736,180 (Spice impregnated edible wrapping foil); U.S. Pat. No. 5,520,925 (Material on the basis of collagen fibers for covering wounds); U.S. Pat. No. 5,190,810 (Composite for use in making protective articles for use in laser surgery); U.S. Pat. No. 5,103,816 (Composite for use in making protective articles for use in laser surgery); U.S. Pat. No. 5,028,695 (Process for the manufacture of collagen membranes used for hemostasis, the dressing of wounds and for implants); U.S. Pat. No. 4,131,650 (Collagen foil for cosmetic application).
As illustrated in the above-listed '180 patent, some edible collagen foils are known for, among other uses, wrapping food products, such as hams.
Collagen foils can be made from a variety of animal skins. However, making collagen foils from porcine skins (i.e., pig skins) presents a number of unique problems over making such from, for example, cattle or bovine. For instance, problems result from the need to remove the porcine hair and to handle the high fat content of porcine skins.
Currently, there are some procedures for preparing collagen foils from porcine skins, but these procedures are not satisfactory for the preparation of food products and the like from the collagen foil produced. The existing procedures focus on the preparation of the porcine skins for the creation of “leather” goods that are processed at tanneries or the like.
Currently, collagen foils are prepared from porcine skins as set forth in paragraphs (a)–(c) below. The present invention is a great advancement over existing procedures. Specifically, existing procedures utilize the following steps:
(a) Porcine skins are collected from an abattoir (i.e., an establishment for slaughtering) and are usually preserved with sodium chloride and sold via skin traders to tanneries (i.e., establishments for converting skins into leather). At the tanneries, the goods are first washed with water and wetting agents and, if necessary, enzymes are also used to remove adhering feces and sodium chloride. During additional steps, hair is removed from the skins using sodium sulfide and lime and, if necessary, using enzymes and lubricants. As a result, the skins (which are alkalinic) are swollen to approximately 5–10 mm thick.
(b) To further process the skins into leather, the skins are horizontally “split” into two layers. The lower layer, i.e., that which is directed toward the animals's body, serves as the starting material for the manufacture of collagen foils. Depending upon the tannery, as an intermediate step, the material can often be stored for an indefinite period in hygienically uncontrolled conditions.
(c) The “splits” are then subjected to a solution of caustic soda and/or lime in an alkalinic hydrolyzation process that can last for up to about 15 days. Through the hydrolyzation process, the material becomes prepared for additional steps, particularly mincing. Due to the molecular characteristics of the bovine skin collagen used (reticular network), hydrolyzation processes ranging from intense to aggressive are required. After the alkalinic hydrolyzation, the splits are brought to a pH<3.5, after having first undergone a strong acidic treatment, e.g., with hydrochloric acid, and then they are ground to a gel-like mass. Or, after alkalinic treatment, the skins are brought to a pH of 5–7 using organic or inorganic acids, ground to a fibrous pulp, and then brought to a pH of <3.5. The fluid pulp, which contains less than 2.5% collagen, and to which other materials, such as glycerin, Karion® (sorbitol), and cross linking agents have been added, is extruded and dried in a band dryer to the foil.
The above-described procedures have significant disadvantages. Overall, the present inventors have found that the foregoing procedures are not satisfactory for foodstuffs and the like. The present inventors have noted that the foregoing procedures have, for example, the following particular disadvantages:    The preserving salts can have additives that should not appear in food.    The skins are not cleaned and are stored with fecal contamination.    The goods can be of questionable origin (i.e., in the trade of skins, there are also goods of questionable origin, such as, e.g., skins from knackeries).    The processing in the tannery is based on the requirements for leather production using technical chemicals.    The product is transported in a non-refrigerated state to the foil manufacturers. As a result, in the warmer seasons, there is the potential for increased bacterial contamination. This contamination can even be substantial enough to cause partial putrefaction of the material delivered. The alkaline product can also potentially undergo uncontrolled chemical decomposition, depending on the conditions of temperature and the time interval between the splitting and the delivery to the foil manufacturers.    The raw material for the foils is subjected to extreme deviations in quality due to the complex series of events that take place.    The aggressive alkalinic treatment (hydrolyzation) also leads to denaturing alterations in the collagen.